Piston diaphragm pump



Nov. 28, 1967 R ACKER ET AL PISTON DIAPHRAGM PUMP 3 Sheets-Sheet 1 FiledNov. 4, 1966 \N \m D.) MN

INVENTOR. lP/Cf/APD C.- 464 6? fa'afaa v Nov. 28, 1967 PISTON DIAPHRAGMPUMP 5 Sheets-Sheet 2 Filed Nov. 4, 1966 .3 M W m M i T M a N 6 6 r w 71 A m M p Wm mm r .e M Y B W W W 5 w 3 M W 5 a 5 w ar r HJM t Nov. 28,1967 ACKE'R ET AL 3,354,831

PISTON DIAPHRAGM PUMP' I 3 Sheets-Sheet 3 Filed Nov. 4, 1966 INVENTORS2/61/44 0 6 461/52 4* UGM an /wax United States Patent 3,354,831 PESTONDIAPHRAGM PUMP Richard C. Acker, Chagrin Falls, and Eugene llahniuk,

Gates Mills, Ohio, assignors to The Weatherhead Company, Cleveland,Ohio, a corporation of Ohio Filed Nov. 4, 1966, Ser. No. 604,502 12Claims. (Cl. 103-44) ABSTRACT OF THE DISCLOSURE A diaphragm pump inwhich a diaphragm is moved by a Working fluid on one side to vary thevolume on the other side of the diaphragm to force the fluid beingpumped in and out through inlet and outlet check valves. The workingfluid is forced against the diaphragm by a cup-shaped piston acting in acylinder and the chamber containing the diaphragm is provided withcylindrical recesses which cooperate with backing plates clamped on eachside of the diaphragm to positively limit the axial movement of thediaphragm. The diaphragm is formed of a layer of resilient rubbermaterial on the working fluid side and a layer of chemically resistantmaterial on the pumping chamber side. In the central portion between thetwo plates, a layer of stiff plastic material is placed between the twodiaphragm layers to control the flexing of the diaphragm. A spring islocated within the pumping chamber to bias the diaphragm to a bottomingposition where it rests on projections so that the working fi-uid actson the full area of the diaphragh at all times. The diaphragm is mountedso that the central portion is stretched over an annular projection toprestress the diaphragm so that it is radially stressed at all times inits range of movement.

This is a continuation-in-part of the co-pending application of RichardC. Acker, Ser. No. 520,464, filed Jan. 13, 1966, now abandoned. Thisinvention relates generally to pumps and more particularly to positivedisplacement pumps particularly adapted to transfer corrosive fluids.

When conventional positive displacement pumps are used with corrosivefluids, numerous problems are encountered. For example, it is necessaryto use corrosion resistant materials for those parts in contact with thefluid, and such materials having sufficient strength are quiteexpensive. It is also necessary to prevent leakage of the corrosivematerial and contamination of the pump lubricant. Further, manycorrosive fluids have a low degree of lubricity which tends to cause ahigh rate of wear between the moving parts of the pump.

One arrangement for overcoming these problems is to isolate thecorrosive fluid from the moving parts by the use of a diaphragm and tooscillate the diaphragm by means of a piston acting on a non-corrosiveactuating fluid such as oil in the space between the piston and thediaphragm.

One important application for pumps of this type is in a central airconditioning system operating on an absorption cycle and employing forits refrigerant a corrosive liquid such as an ammonia water solution.When air conditioning systems of this type are installed in homes andofiices, the pump must meet a number of critical requirements andconditions. Because the pump is usually installed very close toinhabited areas, it is extremely important that the pump have a highdegree of reliability against leakage of the solution which would resultin the release of ammonia gas. In addition, the pump must be able todeliver a high volume and operate at a relatively low noise andvibration level. Also, the requirements of such refrigeration systemsand the physical arrangement of the equipment often requires that thepump cannot be located in the optimum position with respect to the restof the system so that it may have to operate at a relatively low inletpressure. Another important problem is presented with the use of anammonia water solution because sudden changes in the pressure of thefluid tend to cause the ammonia gas to vaporize and form bubbles withinthe liquid. This occurrence tends to result in hammering and noise whenthe liquid is placed under pressure.

In accordance with the preferred embodiment of this invention, the aboveand other problems have been solved or minimized by providing a pumphaving a pair of opposed cylinders within which slides a singledouble-ended piston oscillated by a scotch yoke drive to minimizeacceleration and to reduce noise and vibration. Each cylinder is closedoff at the outer end by means of a flexible diaphragm and a head havinginlet and outlet valves therein. The pistons are substantially hollow soas to allow a large fluid space within the piston and cylinder foractuation of the diaphragm. The hollow pistons are provided with bleedopenings to insure positive filling of the cylinders with the workingfluid or oil present within the housing and to allow escape of anyentrapped air within the oil. The maximum pressure of the oil acting onthe diaphragm is controlled by means of a relief valve adapted to ventthe working fluid from the diaphragm if the outlet pressure of theammonia water solution rises above a predetermined level.

For long life, the diaphragm extends over a rounded annular projectionwhich prestresses the diaphragm to prevent any flexing or folding as thediaphragm oscillates. To avoid any corrosive action by the ammonia watersolution, the diaphragm is made of at least two layers, the one next tothe corrosive fluid being of an inert and chemically resistant materialsuch as polytetrafluoroethylene and the one next to the oil being ofrubberized fabric to give the diaphragm tensile strength and assure along flex life. The flex life of the diaphragm can be further increasedby the addition of a layer of a stiif yet relatively flexible materialsuch as nylon between the chemically resistant layer and the rubberizedfabric to prevent extrusion of portions of therelatively soft chemicallyresistant layer over an extended period of operation.

The chamber within the head and the diaphragm support plate are arrangedso as to insure a minimum clearance volume, and a positive spring returnis provided for the diaphragm to insure positive filling of thediaphragm chamber even under extremely low inlet pressures. By thecombination of the positive diaphragm return, the low clearance volumeand the harmonic oscillation provided by the scotch yoke drive, anytendency of the ammonia to vaporize and produce hammer and vibration isgreatly reduced. Furthermore, the start-up noise had been reduced byproviding means to assure that the areas on opposite sides of thediaphragm assembly exposed to the oil and to the ammonia water solutionare substantially the same so as to minimize any tendency for pressurepeaks to occur in the oil before the initial movement of the diaphragmassembly during start-up. Also, the use of a single piston member with ascotch yoke drive not only allows the pump to be quite compact in sizewithout sacrificing pump capacity but also provides the maximumsimplicity necessary for low cost of manufacture and long operating lifewith a minimum of maintenance.

Additional features and advantages of the pump of the present inventionwill readily become apparent upon an examination of the drawings and thefollowing detailed description of the preferred embodiment of theinvention.

In the drawings:

FIGURE 1 is a partial longitudinal cross-sectional View of a pumpconstructed in accordance with the present invention;

FIGURE 2 is a cross-sectional view taken along the axis of the driveshaft;

FIGURE 3 is a fragmentary view showing the clamping arrangement used tomount the diaphragm;

FIGURE 4 shows a modification of the diaphragm assembly, its clampingarrangement and the diaphragm cavity; and

FIGURES 5 through 7 each show different alternative means for spacingthe support plate of the diaphragm assembly from the housing.

Referring to the drawings in greater detail, the pump comprises ahousing 10 having a pair of end portions 11 and 12 and defining a fluidcavity 13. Extending outwardly from the fluid cavity 13 through the endportions 11 and '12 are a pair of cylinder bores 17 and 18 respectively.

In order to facilitate the assembly of the pump, the housing 10 isdivided into a body section 19 and a cylinder section 20 securedtogether by a plurality of bolts (not shown) and sealed by a gasket 21.

-A pair of head members 23 and 24 are secured to the end portions 11 and12 respectively of the housing 10 by aplurality of bolts 25. Each headmember is provided with an inlet passage 26 and an outlet passage 27.Each inlet passage is connected to the radial inner face of itsassociated head member by an axially extending counterbore having anenlarged portion 31. Each outlet passage 27 is also connected to theradial inner face of its associatedhead member by a counter-bore 34having an enlarged portion 35. The head members 23 and 24 aresubstantially identical, the only difference being that the counterbores30 and 34 on the head member 24 are drilled all the way through thebosses 36 and 37 and tapped to provide the pump with an inlet opening 40and an outlet opening 41.

The inlet passages 26 in the head members 23 and 24 are interconnectedby a transfer tube 44. The ends of the transfer tube 44 are disposedwithin the enlarged portions 31 of the counterbores 30 and sealedtherein by O-ring seals 46. A similar transfer tube 45 disposed withinthe counterbores 34 and sealed therein by O-rings 47 interconnects theoutlet passages 27 of each head member.

A drive shaft 50 extends through the fluid cavity 13 perpendicular tothe axis of the cylinder bores 17 and 18. On one end of the 'drive shaft50 is formed a drive portion 51 which extends beyond the housing 10 (seeFIG- URE 2) and is adapted to be connected to an electric motor or othersuitable power source (not shown). The drive shaft is also provided witha first bearing portion 52, a crank portion 53 eccentric to the firstbearing portion 52, and a second bearing portion 54 concentric with butof a smaller diameter than the first bearing portion 52.

The drive shaft 50 is rotatably mounted within the body section 19 ofthe housing 10 by a ball bearing assembly 57 disposed about the firstbearing portion 52 and a needle bearing assembly 58 disposed about thesecond bearing portion 54. The ball bearing assembly 57 is slidablyreceived within a bore 63 formed in the body section 19 and the needlebearing assembly 58 is press fitted within a counte-rbore 64 formed inthe body section 19 on the opposite side of the fluid cavity 13. Theball bearing assembly 57 is retained on the shaft against axial movementby a pair of split realigning rings 59 disposed within a pair of groovesformed on the outer surface of the shaft 50. This permits removal of thedrive shaft 50 and ball bearing assembly 57 as a unit and gives freeaccess to the parts located in the fluid cavity 13.

The drive shaft 50 is secured within the body section 19 by an annularspacer 65 which is disposed within the bore 63 in abutting engagementwith the ball bearing assembly 57. A split retainer ring 66 is disposedin a groove 67 in the outer end oft-he bore 63 and retains both i thespacer 65 and the ball bearing assembly 57 within the bore 63. The bore63 is sealed by an O-ring 68 disposed in a recess 69 about the outerperiphery of the spacer and by a packing ring or shaft seal 70 disposedbetween 4 the inner periphery of the spacer 65 and the first bearingportion 52.

In order to ventilate the fluid cavity 13 and allow replenishment of thehydraulic fluid, a vent cap is attached to the body section 19. The ventcap 75 is connected to the fluid cavity 13 through a passage 76 shown inFIGURE 2.

An elongated piston block 80 is centrally disposed within the fluidcavity 13. The piston block 80 includes a central portion 81 and a pairof cup-shaped piston portions 82 and 83 formed on its opposite ends. Thepiston portions 82 and 83 are received within the cylinder bores 17 and18 in the housing 10.

A scotch yoke drive arrangement is used to impart a harmonic motion tothe piston portions 82 and 83 as they reciprocate in the cylinder bores17 and 18. The scotch yoke drive includes a bearing block 84 having abore 85 in which the crank portion 53 of the drive shaft 58 is rotatablyjournalled.

The bearing block 84 is slidably disposed within a vertical bearingblock slot 88 formed in the central portion 81 of the piston block 88.In order to allow the eccentric crank portion 53 of the drive shaft 50to rotate relative to the vertically fixed piston block 80, the driveshaft extends through an enlarged opening 89 formed through the centralportion 81 of the piston block 80 on opposite sides of the bearing blockslot 88.

As the drive shaft 50 rotates, the piston block 80 is horizontallyreciprocated by the bearing block 84. Since the bearing block 84 islimited to a vertical sliding motion relative to the piston block 80 bythe bearing block slot 88, the eccentric motion of the crank portion 53imparts a horizontal motion to the piston block 80.

The cup-shaped piston portions 82 and 83 are formed with recesses 86 and87 adjacent the central portion 81 to minimize the reciprocating massand insure a maximum volume of fluid Within the working chamber.Adjacent the rear of each of the piston portions 82 and 83 is formed aplurality of radial ports 92 extending from the exterior into therecesses 86 and 87. These ports are uncovered and establishcommunication between the fluid cavity 13 and the recesses of the pistonportions as the associated piston portion approaches the innermostextent of its intake stroke. In FIGURE 1, the piston block 80 is shownin -a mid-point position and both sets of ports 92 are therefore closed.The purpose of these ports is to allow any entrapped air to escape fromwithin the piston portions and to allow fluid from the fluid cavity 13to flow into the piston portions to make up for any fluid lost byleakage.

Since both sides of the pump are identical in structure and mode ofoperation, only the right side as seen in FIGURE 1 will be described infurther detail. The inner radial face of the head member 24 and the endportion 12 of the cylinder section 20 cooperate to form a diaphragmcavity 95. The diaphragm cavity 95 is divided by a diaphragm assembly 96into a working fluid chamber 97 to the left of the diaphragm assembly 96and a pumping fluid chamber 98 to the right of the diaphragm assembly96.

The Working fluid chamber 97 opens into the cylinder bore 18. At the topof the working fluid chamber 97 is an external filling port 99 closed bya plug 100. A relief check valve assembly 103 is mourned in the cylindersection 20 and connected to the bottom of the working fluid chamber 97through a passage 102. Should a pressure build-up occur in the workingfluid chamber 97 a ball type valve 105 in the relief valve assembly 103is forced open against the load of spring 104 and the fluid from theworking fluid chamber is bled back into the fluid cavity 13. The workingfluid chamber 98 is connected to the inlet passage 26 by a pressureresponsive poppet type inlet valve assembly 106 and to the outletpassage 27 by a pressure responsive poppet type discharge valve assembly110.

In order to obtain a diaphragm that is both resilient and impervious toattack by the corrosive fluid being pumped, the diaphragm assembly 96includes a laminated diaphragm 115. Referring to FIGURE 3, the side ofthe diaphragm 115 which is exposed to the non-corrosive working fluidcomprises a layer of a resilient material 116 such as a rubber orneoprene impregnated fabric while the side which is exposed to thecorrosive fluid being pumped comprises a layer of a highly chemicallyresistant material 117 such as polytetrafluoroethylene.

To support the central portion of the diaphragm 115, the diaphragm issandwiched between a support plate 129 on its left side and a back upplate 121 on its right side as shown in FIGURE 3. The support plate 120and the back up plate 121 are secured together by a rivet 122 extendingthrough the diaphragm 115. To prevent leakage around the rivet, a sealis formed between the rivet 122 and the back up plate 121 as by weldingthe head of the rivet to the back up plate as shown at 123 or by anyother suitable sealing means.

To minimize any tendency of the diaphragm 115 to tear around the rivet122 and to aid in sealing between the support plate 120 and the back upplate 121, a series of cooperating annular ribs 124 and 125 are providedon the support plate and the back up plate respectively. Both thesupport plate 120 and the back up plate 121 are axially offset slightlyat a point radially outwardly of the rib 125 to provide clearance oneach side of the diaphragm 115. The clearance prevents binding of thediaphragm by the plates 128 and 121 thereby assuring that a greaterradial extent of the diaphragm will be in tension than if the diaphragmwere clamped between the plates 120 and 121 all the way to their outerperiphery. Thus, the flexing action of the diaphragm is distributed overa greater area and the life of the diaphragm is lengthened.

A return spring 128 is provided between the back up plate 121 and theinner surface of the head member 24. The return spring 128 biases thediaphragm assembly 96 toward the piston portion 83 and into engagementwith the stop surface 129 on the cylinder portion 20. Thus, the returnspring 128 aids the piston portion 83 in moving the diaphragm assemblyto the left in the diaphragm cavity 95 during the intake stroke tomaximize the volume of the pumping chamber 98 and to assure a partialvacuum in the pumping chamber. By using the return spring 128, it ispossible to obtain the maximum possible pressure differential across theinlet valve assembly 106 with a given inlet head. This is important whenthe pump must be mounted in a position relative to the remainder of thesystem which tends to reduce the inlet head to the pump. The returnspring 128 is retained in a centered position on the back up plate 121by a washer 126 secured to the back up plate.

Referring to FIGURE 3, the diaphragm is shown at its neutral ormid-point of oscillation while the phantom lines 130 and 131 illustratethe two extreme positions of oscillation. The diaphragm 115 is mountedwithin the diaphragm cavity 95 by having its outer periphery clampedbetween a clamping face 132 on the cylinder section 20 and a clampingface 133 on the head member 24. An O-ring 134 is disposed in a groove135 in the clamping face 133 to form a seal between the outer layer ofchemically resistant material 117 on the diaphragm 115 and the headmember. To assure a seal and a positive grip between the clamping faces132 and 133, a set of cooperating annular ribs 136, 137 and 138 areformed on the clamping faces 132 and 133 respectively.

A recess 139 is provided immediately adjacent the rib 137. The recess139 receives any material extruded from between the clamping faces 132and 133 when the outer periphery of the diaphragm 115 is clampedtherebetween and serves as a relief to avoid any pressure on thediaphragm at this point.

A rounded annular protuberance 142 is formed on the end face of the endportion 12 immediately adjacent the recess 139. The rounded protuberance142 extends axially beyond the clamping face 132 and terminates in anaxially and radially inwardly tapering face 143. At 144 the radial endface of the head member 24 tapers radially and axially inwardly of thehead member from a point approximately opposite the mid-point of therecess 139 to a point opposite the tapered face 143 and below therounded protuberance 142. Because of the tapered face 144, the diaphragm115 is not clamped between the rounded protuberance 142 and the headmember 24 but is offset with respect to the clamped portion. Thus, atthe mid-point of oscillation or in the absence of the return spring 128,the remaining or unclamped portion of the diaphragm which divides thediaphragm cavity 95 is axially offset with respect to the portionclamped between the faces 132 and 133. This offsetting of the twoportions of the diaphragm subjects the unclamped portion to a smallinitial stress.

By prestressing the unclamped portion of the diaphragm 115, theunclamped portion is not subjected to a compressive stress when thediaphragm passes through its neutral mid-point as it oscillates in thediaphragm cavity 95. Since the compressive stresses in the unclampedportion are minimized, the tendency for the diaphragm to develop foldsin the unclamped forward portion along which the diaphragm may tear andfail is minimized.

Another important advantage of the rounded protuberance 142 is that itallows the stresses at the outer pe riphery of the diaphragm 115 to bedistributed over a relatively large area with a rolling motion as thediaphragm oscillates. This prevents the stresses at the outer peripheryof the unclamped portion from being concentrated along an annular lineseparating the clamped from the unclamped portions of the diaphragm.Since the stresses are not concentrated in an annular line, the tendencyfor the diaphragm to tear and fail along such a line adjacent theclamping faces is also minimized.

Operation The fluid cavity 13 is filled through the opening for the ventcap with a non-corrosive working fluid such as an oil having sufiicientlubricity to lubricate the moving parts of the pump. The working fluidchambers 97 are filled by removing the plug 100 and introducing theWorking fluid through the filling port 99 as the drive shaft 50 isslowly rotated to move the piston portions 82 and 83 back and forth inthe cylinder bores 17 and 18.

The corrosive fluid to be pumped enters the pump through the inlet port40 and flows through the counterbore 30 into the inlet passage 26 in thehead member 24 and through the transfer tube 44 into the counterbore 30and inlet passage 26 in the head member 23.

As the drive shaft 50 rotates, the rotary motion of the eccentric crankportion 53 is translated into a horizontal reciprocation of the pistonblock by the bearing block 84 sliding vertically in the bearing blockslot 88. On the intake stroke, the piston portion 83 moves to the leftin the cylinder bore 18 exerting a partial vacuum on the fluid in theWorking fluid chamber 97. This in conjunction with the action of thereturn spring 128 moves the diaphragm assembly 96 to the left in thediaphragm cavity creating a partial vacuum in the pumping chamber 98.

The partial vacuum in the pumping chamber 98 creates a pressurediflerential across the inlet valve assembly 106. When the pressuredifferential is greater than the force exerted by the spring 107, thepoppet inlet valve 108 is forced open by the pressure of the fluid inthe inlet passage 26 and the fluid flows into and fills the pumpingchamber.

7 and the fluid is discharged into the outlet passage 27 and out of thepump through the outlet port 41.

During the operation of the pump, the ports 92 are uncovered each timethe piston portion 83 nears the innermost extent of the intake stroke.This allows any entrapped air to escape from the interior of the pistonportion 83 and for fluid from the fluid cavity 13 to flow into theworking fluid chamber '97 to replace the fluid lost by leakage.

Should an excessive pressure build-up occur in the working fluid chamber97 during a discharge stroke of the piston portion 83, the ball checkvalve 105 is forced outwardly against the spring 104. This allows theexcess pressure in the working fluid chamber 97 to bleed back into thefluid cavity 13 through the passage 102 and the relief valve assembly103.

FIGURE 4 illustrates a modified embodiment of the diaphragm assembly andits clamping arrangement. In the embodiment of FIGURE 4, the end portion12, head rnember 24' and diaphragm assembly 96 are, except as describedhereinafter, generally similar to those illustrated in the embodiment ofFIGURE 3 with the diaphragm assembly 96' including a layer of resilientmaterial 116' and a layer of chemically resistant material 117 as in theembodiment of FIGURE 3.

Under certain conditions, when the chemically resistant layer 117' ofthe diaphragm 115' is of a relatively soft material there may be atendency for the material to be extruded into the clearance spacebetween the outer periphery of the back-up plate 121' and the wall ofthe pumping chamber 98' by the action of the layer 116. After anextended period of operation this extruded portion may tear and thediaphragm fail.

The modified diaphragm construction illustrated in FIGURE 4 minimizesthe extrusion of the layer 117 and substantially increases the operatinglife of the diaphragm. In order to prevent extrusion of the layer 117',a stiffer reinforcing disc 119 of a deformation resistant yet relativelyflexible material such as nylon is interposed between the centerportions of the layers 116 and 117.

This disc provides additional support for the layer 117', and reducesthe tendency of the backing layer 116 to deform and force the layer 117into the clearance space when the diaphragm assembly 96' is moved to theright under the action of the working fluid. The diameter of the disc119 is substantially at least as great as that of the pumping chamber98'. Preferably, however, the diameter should be slightly greater thanthat of the pumping chamber 98 in order to assure adequate support ofthe layer 117.

Also illustrated in the embodiment of FIGURE 4 is a modified clampingarrangement for the diaphragm assembly 96'. The modified clampingarrangement includes a pair of annular recesses 140 and 141 in thehousing end portion 12' and the head member 24 respectively. Theserecesses 140 and 141 receive any material displaced when the outerperiphery of the diaphragm 115' is clamped between the clamping faces132' and 133 to relieve any uneven forces which may be exerted upon theend portion 12 and the head member 24' by the deformation of the outerperipheral portion of the diaphragm 115.

The support apparatus for the central portion of the diaphragm 115' isalso slightly modified in the embodiment illustrated in FIGURE 4. Inthis embodiment the support plate 120' and the back-up plate 121 areclamped against the diaphragm 115' by a bolt 122 and a cooperating nut145 which bears against a washer 146 on the outer surface of the supportplate 120. The head of the bolt 122' is sealingly secured to the washer126' as by Welding or brazing at 123'.

In this embodiment the support plate 120 is provided with a singleannular rib 124 and the back-up plate 121 is provided with a pair ofradially spaced annular ribs 125' and 125. Also in this embodiment thesupport plate 120'. and the back-up plate 121' are not axially offset toprovide the clearance along the diaphragm 115 as in the embodiment ofFIGURE 3. In the embodiment of FIG- URE 4, an adequate clearance isprovided between the diaphragm 115' and the plate 126' and 121 byutilizing the inherent resistance to deformation of the diaphragm 115 bythe ribs 124, 125 and 125 when the nut 146 is tightened to keep theplates 120' and 121' spaced apart a distance greater than the thicknessof the diaphragm 115'.

As the nut 146 is tightened and the plate 120 and 121' move together theribs 124, 125' and 125" deform the diaphragm 115. Since these ribs areblunt, the diaphragm 115 will not be deformed sufliciently to allow theentire radial extent of the plates 120 and 121 to clamp the diaphragm115. Thus, an adequate clearance is provided between the diaphragm 115'and the plates 120' and 121' in the area extending radially outwardlyfrom the rib 125. The diaphragm material will also be deformed radiallyinwardly by the ribs 124 and 125" and will tend to fill the spacebetween the rib 124', 125 and the shank of the bolt 122'. This tends tolimit further deformation of the diaphragm 115 and forms a seal aroundthe shank of the bolt 122.

Under certain operating conditions, notably after the pump has been atrest for a period of time, the pump of the embodiment shown in FIGURE 3may produce an objectionable noise as it starts up. This noise isproduced by the occurrence of high pressure peaks in the working fluidprior to the initial movement of the diaphragm assembly 96.

In the arrangement of FIGURE 3 after the pump has been at rest for aperiod of time with the fluid being pumped still under pressure, astable condition is reached wherein the support plate 120 of thediaphragm assembly 96 is resting against the stop surface 129. Thisdrift of the diaphragm assembly 96 to the left within the diaphragmcavity 95 from the centered or neutral position is produced by a numberof factors including the action of the pressurized fluid being pumpedand the spring 128 (not shown in FIGURE 3) upon the right hand side ofthe diaphragm assembly 96. These factors result in the exertion ofenough force on the diaphragm assembly 96 to pressurize the workingfluid within the working fluid chamber 97. After a period of time theworking fluid is forced through the clearance between the piston portion83 and the wall of the cylinder bore 18 into the fluid cavity 13 whichis at atmospheric pressure because of the vent and the diaphragmassembly 96 drifts to the left until it engages the stop surface 129.

In this stable condition the support plate 120 tends to form a seal withthe stop surface 129 around the outer edge of the cylinder bore 18. Whenthe pump is started up movement of the piston portion 83 to the rightincreases the pressure of the working fluid within the cylinder boreportion of the working fluid chamber 97 and because of the seal formedby the support plate 120 around the outer edge of the cylinder bore 18,this pressure acts upon the diaphragm assembly 96 over an area onlyequal to the cross-sectional area of the cylinder bore 18. Since thefluid being pumped in the pumping fluid chamber 98 acts on a muchgreater area on the dia phragm assembly 96 relatively high pressurepeaks occur in the cylinder bore 18 before initial movement of thediaphragm assembly 96 to the right within the diaphragm cavity canoccur. The resulting hammering sound created by these high pressurepeaks produces a disturbing noise level in the surrounding environment.If initial start up piston movement is to the left, a vacuum conditionin chamber 95 results which causes high start up torque requirements,noise and release of entrapped air from the working fluid.

It was found that the start up noise could be reduced if the supportplate were not allowed to engage the stop surface 129 in such a manneras to form a seal with it or around the outer edge of the cylinder bore18.

9 Several arrangements are shown in FIGURES 4 through 7 for overcomingthis problem.

In the embodiment of FIGURE 4 stop surface 129 is provided with aplurality of radially extending grooves or channels 150 which interruptthe area of engagement between the stop surface and the support plate.The grooves 150 prevent a seal from tending to be formed and allow thepressure of the working fluid to be distributed over the entire leftside of the diaphragm assembly 96' which has an area substantially equalto the area on the right side of the diaphragm assembly acted upon bythe fluid being pumped.

FIGURE 5 schematically illustrates a different alternative arrangementwherein the support plate 120 of the diaphgram assembly 96' is spacedfrom the stop surface 129 by a plurality of pin-like members 152 securedin the housing and disposed circumferentially about the stop surface andextending into the space between the support plate and stop surface.Another and different alternative arrangement is shown in FIGURES 6 and7 wherein a plurality of projections are formed on the support plate 120for spacing a substantial portion of said support plate from said stopsurface. In FIGURE 6 these projections are in the form of a plurality ofcircumferentially spaced annularly extending ribs 154. FIG- URE 7illustrated the projections as being circumferentially spaced radiallyextending ribs 156.

While the preferred embodiments of this invention have been shown anddescribed in considerable detail, it is recognized that the invention isnot limited to the specific forms sho-wn and'described and variousmodifications and rearrangements may be made without departing from thescope of the invention as defined in the following claims.

What is claimed is:

1. A pump comprising a housing member defining a fluid cavity and acylinder bore, a piston in said cylinder bore, drive means toreciprocate said piston, a head member secured to said housing defininga diaphragm cavity at the outer end of said cylinder bore, a diaphragmseparating said diaphragm cavity into working chamber opening to saidcylinder bore and a pumping chamber, said diaphragm being 'of alaminated construction having a first layer of resilient elastomericmaterial and a second layer of a highly chemically resistant materialexposed to the fluid in the pumping chamber, said diaphragm having arelatively stiff reinforcing disc disposed between said first and secondlayers, said disc having an outer diameter substantially at least asgreat as the diameter of said pumping chamber, mounting means securingthe outer periphery of said diaphragm to one of said members including apair of opposed clamping faces, one of said clamping faces having arounded annular protuberance adjacent its inner periphery extendingaxially beyond said clamping face and the other of said clamping faceshaving a recessed surface adjacent its inner periphery opposite saidprotuberance, said mounting means being so constructed and arranged thatwhen said diaphragm is clamped between said clamping faces saidprotuberance and said recessed surface are axially separated from oneanother by at least substantially the thickness of said diaphragm, saidprotuberance axially of setting the unclamped from the clamped portionsof said diaphragm and thereby prestressing the unclamped portion, inletand outlet ports opening into said pumping chamber, and valve means insaid inlet and outlet ports, whereby reciprocation of said piston actsupon fluid within said working chamber and imparts oscillation to saiddiaphragm to draw fluid into and force fluid out of said pumpingchamber.

2. A pump as set forth in claim 1 wherein said reinforcing disc is of anylon material.

3. A pump comprising a housing member defining a fluid cavity and acylinder bore, a piston, a head member secured to said housing defininga diaphragm cavity at the outer end of said cylinder bore, a diaphragmseparating said diaphragm cavity into aworking chamber opening into saidcylinder bore and a pumping chamber, mounting means securing the outerperiphery of said diaphragm to one of said members including a pair ofopposed annular clamping faces defining an annular clamping zone, one ofsaid members having a rounded annular protuberance radially inward ofsaid clamping zone extending axially beyond said clamping face and theother of said members having a recessed surface radially inward of saidclamping zone opposite said protuberance, said mounting means being soconstructed and arranged that when said diaphragm is clamped betweensaid clamping faces at said clamping zone said protuberance and saidrecessed surface are axially separated from one another by at least thethickness of said diaphragm, said protuberance axially offsetting theunclamped from the clamped portions of said diaphragm and therebyprestressing the unclamped portion so that said diaphragm is radiallystressed at all times, inlet and outlet ports opening into said pumpingchamber, and valve means in said inlet and outlet ports, wherebyreciprocation of said piston acts upon fluid within said working chamberand imparts oscillation to said diaphragm to draw fiuid into and forcefluid out of said pumping chamber.

4. A pump as set forth in claim 3 wherein the center section of saiddiaphragm is provided with a support plate on the working chamber sideand a back-up plate on the pumping chamber side, and meansinterconnecting said suppoit plate and said back-up plate to clamp saiddiaphragm therebetween.

5. A diaphragm mounting arrangement including a first member having afirst annular clamping face, a second member having a second annularclamping face of substantially the same radially dimensions as saidfirst clamping face, means securing said first and second memberstogether with said first and second clamping faces being axially opposedto and facing one another to define an annular clamping zone, adiaphragm having a portion of its outer periphery clamped between saidfirst and second clamping faces at said clamping zone, a rounded annularprotuberance on said first member radially inward of said clamping zoneprojecting axially beyond said'first clamping face toward said secondclamping face, said second member having a recessed surface radiallyinward of said clamping zone and axially opposite said annularprotuberance and spaced therefrom by a distance greater than thethickness of said diaphragm whereby the unclamped portion of saiddiaphragm is axially offset from said clamped portion and said unclampedportion is thereby prestressed at all times.

6. A device as set forth in claim 5 wherein an annular recess isprovided in 'saidfirst member radially between said clamping zone andsaid annular protuberance.

7. A pump comprising a housing member defining a fluid cavity and acylinder bore, a piston in said cylinder bore, drive means toreciprocate said piston, a head member secured to said housing anddefining a diaphragm cavity at the outer end of said cylinder bore, adiaphragm assembly separating said diaphragm cavity into a workingchamber opening into said cylinder bore and a pump ing chamber, wherebyreciprocation of said piston acts upon fluid within said working chamberand imparts oscillation to said diaphragm assembly to draw fluid intoand force fluid out of said pumping chamber, mounting means securing theouter periphery of said diaphragm to one of said members including apair of opposed clamping faces, the center section of said diaphragmbeing provided with a support plate on the working chamber side and abackup plate on the pumping chamber side, means interconnecting saidsupport plate and said back-up plate, said housing defining a stopsurface adjacent the outer end of said cylinder bore, said stop surfaceand said support plate being so constructed and arranged as to engageone another and limit the inward travel of said diaphragm assemblytoward said working chamber, and means 11 adapted to interrupt the areaof engagement between said support plates and said stop means to preventthe support plate and stop surface from forming a continuous sealtherehetween.

8. A pump set as set forth in claim 7 wherein said interrupting meanscomprises a channel in said stop surface communicating at one end withsaid cylinder bore through the wall thereof.

9. A pump as set forth in claim 7 wherein said interruptingmeanscomprises spacer means spacing a substantial portion of said supportplate from said stop surface.

10. A pump as set forth in claim 9 wherein said spacer means comprises aplurality of pin-like members extending into the space between said stopsurface and said support plate.

11. A pump as set forth in claim 9 wherein said spacer means comprises aplurality of projections on said support plate extending toward saidstep surface.

12. A piston-diaphragm pump comprising a housing defining a workingfluid cavity and having a pair of end portions and a pair of cylinderbores extending from said end portions and opening into said fluidcavity, said housing being composed 'of a body section and a removablecylinder section, said cylinder section including one of said endportions and the adjacent cylinder bore, a pair of head members secured.to said housing end portions and defining with each of said end portionsa diaphragm cavity opening into each of saidbores, a flexiblediaphragmin each diaphragm cavity dividing the diaphragm cavity into aworking fluid chamber and a pumping chamber, each diaphragm beingclamped about its outer. periphery between a pair ofclamping facesformed on the adjacent surfaces of the head members and the end portionsof said housing, each of said. head members having an intake port and adischarge port communicating with the pumping chamber, a pressureresponsive intake valve in each of said intake ports and a pressureresponsive discharge valve in each of said discharge ports, transfertube means extending between said head members having passagewaysinterconnecting the intake and discharge ports of one head member withthe respective intake and discharge ports of the other head member, anelongated piston block having cup shaped piston portions on oppositeends thereof and a bearing block slot through the center, the axis ofsaid slot being perpendicular to the longitudinal axis of said pistonportions, each of said cup shaped piston portions having a port formedtherein extending from the exterior to the interior of said cup shapedpiston portion and being so arranged as to be opened and establishcommunication between the working chamber and the fluid cavity as thepiston portion reaches the inward extremity of the intake stroke and tobe closedduring the major portion of the working stroke, a bearing blockslidably ,disposedwithin said :bearin'g block slot and having'a' crankreceiving aperture the outward working stroke of said piston, adiaphragm biasing spring extending between said diaphragm and itsassociated head member and biasing the diaphragm inwardly toward itsassociated piston member, said diaphragm having a laminated constructionwith the major portion being a resilient elastomeric material and thepump fluid exposed surface being a layer of highly chemically resistantplastic material, a pair of diaphragm support plates secured to theopposite faces of said diaphragm and covering the central portion ofsaid diaphragm, stop means immediately adjacent the inner portion of theworking chamber in such a position as to engage one of said supportplates and limit the inward travel of the diaphragm, a rounded axiallyextending annular protuberance on one of said members, about the outerperiphery of said diaphragm cavity and immediately adjacent thediaphragm clamping face, said protuberance extending axially beyondadjacent portion of the clamping face of the member upon which it isformed, said protuberance engaging the diaphragm and offsetting thecenterline of the unclamped from the clamped portion thereby subjectingthe unclamped flexing portion of the diaphragm to a slight initialstress when the diaphragm is in its midpoint position.

References Cited UNITED STATES PATENTS 1,832,259 11/1931 Stephens 103-44 2,301,407 11/1942 Houser et al. 103-44 2,702,006 2/1955 Bachert103150 2,839,002 6/1958 Williams 103-44 X 2,808,484 10/1957 Beck et al200--83 2,919,650 1/1960. Wiggerrnann 10344 3,000,320 9/1961 Ring 103443,075,468 1/1963 Eifel 103-44 3,092,029 6/1963 Hanson et al. 103-150 X3,153,381 10/1964 Holley 103-44 FOREIGN PATENTS 586,862 4/1947 GreatBritain.

ROBERT M, WALKER, Primary Examiner,

1. A PUMP COMPRISING A HOUSING MEMBER DEFINING A FLUID CAVITY AND ACYLINDER BORE, A PISTON IN SAID CYLINDER BORE, DRIVE MEANS TORECIPROCATE SAID PISTON, A HEAD MEMBER SECURED TO SAID HOUSING DEFININGA DIAPHRAGM CAVITY AT THE OUTER END OF SAID CYLINDER BORE, A DIAPHRAGMSEPARATING SAID DIAPHRAGM CAVITY INTO WORKING CHAMBER OPENING TO SAIDCYLINDER BORE AND A PUMPING CHAMBER, SAID DIAPHRAGM BEING OF A LAMINATEDCONSTRUCTION HAVING A FIRST LAYER OF RESILIENT ELASTOMERIC MATERIAL ANDA SECOND LAYER OF A HIGHLY CHEMICALLY RESISTANT MATERIAL EXPOSED TO THEFLUID IN THE PUMP CHAMBER, SAID DIAPHRAGM HAVING A RELATIVELY STIFFREINFORCING DISC DISPOSED BETWEEN SAID FIRST AND SECOND LAYERS, SAIDDISC HAVING AN OUTER DIAMETER SUBSTANTIALLY AT LEAST AS GREAT AS THEDIAMETER OF SAID PUMPING CHAMBER, MOUNTING MEANS SECURING THE OUTERPERIPHERY OF SAID DIAPHRAGM TO ONE OF SAID MEMBERS INCLUDING A PAIR OFOPPOSED CLAMPING FACES, ONE OF SAID CLAMPING FACES HAVING A ROUNDEDANNULAR PROTUBERANCE ADJACENT ITS INNER PERIPHERY EXTENDING AXIALLYBEYOND SAID CLAMPING FACE AND THE OTHER OF SAID CLAMPING FACES HAVING ARECESSED SURFACE ADJACENT ITS INNER PERIPHERY OPPOSITE SAIDPROTUBERANCE, SAID MOUNTING MEANS BEING SO CONSTRUCTED AND ARRANGED THATWHEN SAID DIAPHRAGM IS CLAMPED BETWEEN SAID CLAMPING FACES SAIDPROTUBERANCE AND SAID RECESSED SURFACE ARE AXIALLY SEPARATED FROM ONEANOTHER BY A LEAST SUBSTANTIALLY THE THICKNESS OF SAID DIAPHRAGM, SAIDPROTUBERANCE AXIALLY OF SETTING THE UNCLAMPED FROM THE CLAMPED PORTIONSOF SAID DIAPHRAGM AND THEREBY PRESTRESSING THE UNCLAMPED PORTION, INLETAND OUTLET PORTS OPENING INTO SAID PUMPING CHAMBER, AND VALVE MEANS INSAID INLET AND OUTLET PORTS, WHEREBY RECIPROCATING OF SAID PISTON ACTSUPON FLUID WITHIN SAID WORKING CHAMBER AND IMPARTS OSCILLATION TO SAIDDIAPHRAGM TO DRAW FLUID INTO AND FORCE FLUID OUT OF SAID PUMPINGCHAMBER.